1. Field of the Invention
The present invention relates to a steer-by-wire gear shifter and particularly to means for controlling an actuator which applies an external force for force feedback to a shift knob.
2. Description of the Related Art
FIG. 4 shows a conventional steer-by-wire gear shifter as an example.
This gear shifter comprises: a holder 1; a rotary shaft 2 rotatably held by the holder 1; a shift lever 3 whose bottom is fixed on the rotary shaft 2; a shift knob 4 attached to the top of the shift lever 3; a detecting means 5 for detecting the operational condition of the shift knob 4, namely the amount and direction of rotation of the rotary shaft 2; an actuator 6 which applies an external force for force feedback to the shift knob 4 through the rotary shaft 2 and the shift lever 3; a control section 8 which receives detection signal a from the detecting means 5 and generates and outputs a control signal b for the actuator 6 and a gear shift signal c for a transmission controller 7; and a release switch 9 which unlocks the shift knob 4. For the detecting means 5, a rotary encoder or variable resistor may be used; for the actuator 6, a rotary motor, a linear motor or a solenoid may be used.
In this gear shifter, the control section 8 can calculate the current position of the shift knob 4 from the current value of the detection signal a. Also, when an operator operates the shift knob 4, the detection signal a changes, which suggests into which position the shift knob 4 has been shifted. While the shift knob 4 is being moved from one position to another position, the actuator 6 is driven so that an adequate feeling of resistance can be given to the shift knob 4 to create a clicking sensation at the time of gear shift operation. While a driver is attempting to change the position of the shift knob 4 from one specific range to another, for example, from the P (parking) range to the R (reverse) range, or from the 2nd (second) range to the 1st (low) range, it is possible to prevent him/her from changing the position of the shift knob 4 in that way without operating the release switch 9 by activating the actuator 6 so as to apply an external force to lock the shift knob 4.
Therefore, a driver can use this gear shifter as if he/she were using a conventional mechanical gear shifter.
However, the above conventional gear shifter has the following drawback. Since the actuator 6 is controlled according to a detection signal a which depends on the rotational amount and direction of the rotary shaft 2, it is possible to perform a gear shift operation with the shift knob 4 regardless of the vehicle""s running condition, transmission operating condition or the like after the driver operates the release switch 9 to unlock the shift knob 4.
This means that even while the engine is running at a high speed, it is possible to change the position of the shift knob 4 from the P range to the R range or to the D (drive) range, or from the D range to the N (neutral) range or to the 1st range and so on. Therefore, unless the driver manipulates the shift knob 4 adequately according to the vehicle""s running condition, transmission operating condition or the like, a jack-rabbit start, hard braking, engine idling or other unfavorable situations might occur.
The present invention has been made to solve the above problem inherent in this prior art; the primary object of the invention is to provide a highly operable and reliable shift knob device which provides the shift knob with an operation feeling which differs depending on the vehicle""s running condition and/or transmission operating condition.
In order to solve the above problem, according to one aspect of the present invention, a steer-by-wire gear shifter comprises: a shift knob; an actuator which applies an external force to the shift knob; a control section for the actuator; first detecting means which detects an operational state of the shift knob; and second detecting means which detects a vehicle""s running condition and/or its transmission""s operating condition, wherein the control section generates a control signal for the actuator based on a first detection signal sent from the first detecting means, referring to a second detection signal sent from the second detecting means, if it decides according to the second detection signal that the shift knob has been properly operated, then it gives the shift knob an adequate external force to enable the shift knob to be shifted, and if it decides according to the second detection signal that the shift knob has been improperly operated, then the shift knob is not held in a shift position selected by a driver but it is shifted into another shift position which is accepted according to the second detection signal.
When the actuator which applies an external force to the shift knob is thus controlled according to the control signal which is generated from the first detection signal sent from the first detecting means for detection of the shift knob""s operational state and the second detection signal sent from the second detecting means for detection of the vehicle""s running condition and/or its transmission""s operating condition, the actuator can be controlled in a way which suits the vehicle""s running condition and/or the transmission""s operational condition, so that an improper operation of the shift knob can be prevented and therefore the operability and reliability of the steer-by-wire gear shifter can be increased.
According to another aspect of the present invention, the control section incorporates shift pattern tables which specify one or more gear shift positions which can be selected according to the first and second detection signals.
When the control section is thus provided with shift pattern tables as required, it can issue control signals more easily, which reduces the burden on the control section and makes gear shift operation smoother.